Automated test equipment (ATE) is generally known and is used to verify the operation of digital integrated circuits as well as analog integrated circuits. Generally, ATE designed specifically to test digital integrated circuits are not capable of measuring an analog frequency signal related to the device under test. ATE typically includes a test computer which is connected to the integrated circuit under test. A test program generates test signals or vectors and applies the signals in a pre-programmed sequence to the inputs of the device under test. The test computer then reads the output signals from the integrated circuit under test and compares the same with the stored patterns.
In the functional testing of integrated circuits digital patterns or vectors are applied to circuit inputs and the output signals measured and compared to stored values. A given input state for an integrated circuit should result in a particular output state. A truth table can be used to describe the digital transfer function and the correctness of the signal waveforms on all of the pins is an indication of proper operation of the device under test.